The solvent deuterium isotope effect on the hydroxide-ion-catalyzed conversion of acetaldehyde to its enolate ion

1988 ◽  
Vol 66 (9) ◽  
pp. 2440-2442
Author(s):  
J. R. Keeffe ◽  
A. J. Kresge
Keyword(s):  
Water Molecule ◽  
Proton Transfer ◽  
Isotope Effect ◽  
Deuterium Isotope Effect ◽  
Solvent Isotope Effect ◽  
Fractionation Factor ◽  
Hydroxide Ion ◽  
Solvent Isotope

Rates of proton transfer from acetaldehyde to the hydroxide ion were measured by iodine scavenging in H2O and in D2O solution at 25 °C; the results give the solvent isotope effect [Formula: see text]. This value is somewhat more consistent with an estimate, made using fractionation factor theory, for hydron transfer directly from the substrate to the hydroxide ion than with another estimate, made similarly, for hydron transfer through an intervening water molecule.

Deuterium solvent isotope effect on the basicity of methanol. Deuterium fractionation factor for CH3OL2+ in aqueous solution

1986 ◽  
Vol 90 (4) ◽  
pp. 543-545 ◽  
Author(s):  
Joseph L. Kurz ◽  
Stanley L. Hazen ◽  
Linda C. Kurz
Keyword(s):  
Aqueous Solution ◽  
Isotope Effect ◽  
Solvent Isotope Effect ◽  
Fractionation Factor ◽  
Solvent Isotope

The Mechanism for Hydrolysis of Primary Alkyl Chlorosulfates in Water. The Kinetic Solvent Isotope Effect and the Secondary Deuterium Isotope Effect

1972 ◽  
Vol 50 (3) ◽  
pp. 434-437 ◽  
Author(s):  
E. C. F. Ko ◽  
R. E. Robertson
Keyword(s):  
Isotope Effect ◽  
Sulfonyl Chloride ◽  
Alkyl Halides ◽  
Activation Process ◽  
Deuterium Isotope Effect ◽  
Solvent Isotope Effect ◽  
Temperature Coefficients ◽  
Enthalpy Of Activation ◽  
Solvent Isotope ◽  
Hydrolysis Of

The temperature coefficients of the enthalpy of activation [Formula: see text] for the hydrolysis of the three chlorosulfates, methyl, ethyl, and β-chloro, are shown to have values of −50,−55, and −60 cal deg−1 mol−1; values in the same range as previously reported for the hydrolysis of the sulfonyl chlorides. The corresponding value for the β-methoxy isomer was −40 cal deg−1 mol−1, about the same as found for the p-methoxybenzenesulfonyl chloride. The kinetic solvent isotope effect, however, was significantly lower than reported for the sulfonyl chloride series, being about the same as found for the hydrolysis of the alkyl halides. While some degree of nucleophilic overlap is probably required in the activation process, the requirement here is reduced to about the same level as that for the primary halides, and there is no need to postulate a different mechanism on passing from the methyl to the ethyl member of the series, confirming the earlier conclusion of Buncel and Millington.

Hydrolysis of Sulfamoyl Chlorides. II. Hydrogen Participation in the Hydrolysis of Diethyl and Methylethylsulfamoyl Chlorides

1972 ◽  
Vol 50 (6) ◽  
pp. 946-951 ◽  
Author(s):  
E. C. F. Ko ◽  
R. E. Robertson
Keyword(s):  
Temperature Coefficient ◽  
Isotope Effect ◽  
Mixed Solvents ◽  
Deuterium Isotope Effect ◽  
Solvent Isotope Effect ◽  
Enthalpy Of Activation ◽  
Exclusion Experiments ◽  
Solvent Isotope ◽  
Intermediate Value ◽  
Hydrolysis Of

Diethylsulfamoyl chloride (2) hydrolyzes eight times faster than dimethylsulfamoyl chloride (1). In 2 the secondary deuterium isotope effect was found to be about 2, hence hydrogen participation is important in the hydrolysis of this compound. The temperature coefficient of the enthalpy of activation [Formula: see text] is exceptional (−39 cal mol−1 deg−1) for a reaction presumably following an SN1 mechanism. The kinetic solvent isotope effect was normal for such a mechanism. The corresponding value of [Formula: see text] for the hydrolysis of piperidylsulfamoyl chloride (4) was about the same as found for 2 while the value for the methylethyl isomer (3) was −66 cal deg−1 mol−1, an intermediate value supporting an explanation based on solvent exclusion. Experiments in mixed solvents support the hypothesis that solvent reorganization is the major factor in determining the value of [Formula: see text]for 2 but not for 4.

Solvent and substrate isotope effects on the enolization and carbon-acid ionization of isobutyrophenone

1996 ◽  
Vol 74 (12) ◽  
pp. 2481-2486 ◽  
Author(s):  
J.R. Keeffe ◽  
A.J. Kresge
Keyword(s):  
Isotope Effect ◽  
Isotope Effects ◽  
Isotopic Fractionation ◽  
Medium Effect ◽  
Solvent Isotope Effect ◽  
Fractionation Factor ◽  
Solvent Isotope ◽  
Carbon Acid ◽  
Fractionation Factors ◽  
Acid Ionization

Bromine scavenging was used to measure rates of acid-catalyzed enolization of isobutyrophenone in H2O and in D2O solution and of isobutyrophenone-α-d in D2O solution. The results provide the solvent isotope effect kH +/kD + = 0.56 and the substrate isotope effect kH/kD = 6.2 on the enolization reaction, both of which are consistent with the generally accepted mechanism for this process. The present results in combination with literature information also provide the solvent isotope effect on the enolization equilibrium, KE(H2O)/KE(D2O) = 0.92, and the solvent isotope effect on the ionization of isobutyrophenone as a carbon acid, kaK(H2O)/kaK(D2O) = 5.4, as well as the product of isotopic fractionation factor and medium effect, [Formula: see text], for isobutyrophenone enol and the medium effect, Φ = 0.47, for its enolate ion. The isotope effect on KE is the first ever determined for the keto–enol equilibrium of a simple aldehyde or ketone; its near-unit value is consistent with expectation on the basis of fractionation factors for the species involved. Key words: isobutyrophenone, keto–enol equilibrium, carbon-acid ionization, solvent isotope effects, isotopic fractionation factors.

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